As semiconductor manufacturing technology continues to evolve toward smaller design rules and higher integration densities, the separation between adjacent structures in integrated circuits becomes increasingly smaller. As such, unwanted capacitive coupling can occur between adjacent structures of integrated circuits such as adjacent metal lines in BEOL (back-end-of-line) interconnect structures, adjacent contacts (e.g., MOL (middle-of-the-line) device contacts) of FEOL (front-end-of-line) devices, etc. These structure-related parasitic capacitances can lead to degraded performance of semiconductor devices. For example, capacitive coupling between transistor contacts can lead to increased gate-to-source or gate-to-drain parasitic capacitances which adversely impact the operational speed of a transistor, increase the energy consumption of an integrated circuit, etc. In addition, unwanted capacitive coupling between adjacent metal lines of a BEOL structure can lead to increased resistance-capacitance delay (or latency), crosstalk, increased dynamic power dissipation in the interconnect stack, etc.
In an effort to reduce parasitic coupling between adjacent conductive structures, the semiconductor industry has adopted the use of low dielectric constant (low-k) dielectrics and ultra-low-k (ULK) dielectrics (in place of conventional SiO2 (k=4.0)) as insulating materials for MOL and BEOL layers of ultra-large-scale integration (ULSI) integrated circuits. The advent of low-k dielectrics coupled with aggressive scaling, however, has led to critical challenges in the long-term reliability of such low-k materials. For example, low-k TDDB (time-dependent dielectric breakdown) is commonly considered a critical issue because low-k materials generally have weaker intrinsic breakdown strength than traditional SiO2 dielectrics. In general, TDDB refers to the loss of the insulating properties of a dielectric when it is subjected to voltage/current bias and temperature stress over time. TDDB causes an increase in leakage current and, thus, degrades performance in nano-scale integrated circuits.